A conventional door lock assembly includes a strike plate (keeper plate) which is usually recessed into the facing of the door frame and a dead bolt or handle-actuated latch carried by the door which engages the strike plate and holds the door in its closed position in the door frame. In an effort to make the door plumb, the carpenter who constructs the door assembly usually shims and builds up the facing of the door opening away from the internal wall studs of the door frame in such a manner that a gap is formed between the door frame and the supporting wall studs. As a result of this "gap", the facing and attached strike plate derive little or ineffective horizontal support from the internal wall studs. With the use of a crowbar or similar object a locked door can be broken into by forcing the strike plate in the direction of the gap, that is, away from contact with the extended bolt. The conventional prior art lock mechanisms therefore offers only small resistance to an experienced burglar.